I. Field of the Invention
This invention relates to a new method of combatting insects at the egg level of development, especially eggs of the tobacco budworm (Hellothis virescens; TBW in the abreviated form) at a locus at which there is growing a crop, especially a plantation crop.
The invention relates also to ovicidal compositions used in the invention.
A particular problem among those which farmers have to face is the destruction of cotton fibers by tobacco budworm. This problem is a very important problem because the larvae insect lives a very short time upon the leaves, e.g. about one or two days, and it spends most of its life in the cotton boll where it is protected from outside aggression such as the pesticide action. Thus, it is very important to reach the tobacco budworm at the egg stage before any damage is made to the crop. Thus the invention is also directed to a method of protecting cotton crop.
II Discussion of the prior art
Many insecticides are well known as active ingredients to protect plants against insects. However the compounds which are recommanded purely for their ovicidal action are rather rare, and those which have both an insecticidal and an ovicidal action are also rather rare.
From the activity of a compound on insects (adults or larvae), nothing can be deduced regarding the activity on eggs. For example, insecticides such as carbaryl or phosphate insecticides are not ovicidal. Pyrethroids are not ovicidal either; if they have been sometimes considered as ovicidal, it is just because they are able to kill the larvae when going out from the eggs, but this is not a true ovicidal action. Thiodicarb is considered as having both an ovicidal and an insecticidal action, but it is rather an exception.
Thus, insecticides have been described in patent application WO 91/04965 but it is not possible to know whether they have any ovicidal action for the hereabove given reasons.